Silvio Berlusconi tells supporters that he will remain in politics. Opponents gathered outside the senate called for him to be jailed. Photograph: Eidon/Demotix/Corbis

Showing on a loop on the screens outside Palazzo Grazioli was a compilation of clips that had a strangely retro feel to it. In one, Silvio Berlusconi was laughing with Tony Blair; in another, he was chatting affably with George W Bush. Jacques Chirac, Kofi Annan, even Pope Benedict XVI: the roll call of former leaders went on – and Berlusconi, in a somewhat more youthful guise, was with them all.

Across town, in a historic and at times openly confrontational series of votes, Italian senators were bringing an end to the former prime minister's near two decades in parliament. But, lest anyone think the 77-year-old might take that as his cue to join his old confrères in retirement, he made it clear that, as far as he was concerned, his political career was still very much ongoing.

"Today they [my opponents] are celebrating because they have managed to bring an adversary – an enemy – before the executioner's squad. They are euphoric," he told the supporters who had gathered outside his mansion to hear of his "persecution" by the country's judiciary. "They have been waiting for it for 20 years … But I don't believe they have definitively won the match of democracy and of freedom."

Waving her flag dreamily as the strains of party anthems thundered around Piazza Venezia, Mariella, a fan from the southern region of Calabria, gave her verdict: "It's a coup d'état. Because justice is not a weapon." Rather than consigned to history, she added, Berlusconi was still the man to lead Italy forward. "Even at 76, 77 years old, if he can rouse young people like that, he's the future," she said.

Most Italians disagree with that assessment. As news of the expulsion came through, a group of anti-Berlusconi activists began celebrating outside the senate with spumante (sparkling wine) and chants calling for the former prime minister to be sent to prison. The move ends the partial immunity from which, as a senator, Berlusconi benefited, though his lawyers have dismissed his arrest as a possibility.

The landmark expulsion – confirmed by the senate speaker at 5.42pm after several hours of fractious debate – followed Berlusconi's definitive conviction for tax fraud at his Mediaset television empire on 1 August. He denies any wrongdoing, and ever since, the political debate of Italy – a country in grave need of concerted action to lift it out of its longest postwar recession – has been dominated by the saga.

Though not part of his actual sentence, the ousting was deemed necessary under an anti-corruption law passed last year that prohibits anyone with a conviction of more than two years from holding elected office or standing for office for six years. Berlusconi was also ordered to serve a four-year prison sentence, commuted to one, which will be enforced next year, either as community service or house arrest.

In the senate on Wednesday, centre-left MPs from the Democratic party (PD) combined with the anti-establishment Five Star Movement (M5S) and others to approve the expulsion – to the obvious rage of Berlusconi loyalists. Several of his female senators had come dressed in black, at least one with an armband. At one point, they began chanting "Silvio, Silvio".

The vote attracted some of the recently appointed senators-for-life, among them the architect Renzo Piano.

In a defiant address that sounded much like an election campaign speech, Berlusconi acknowledged that the expulsion – one of the heaviest blows in his eventful political career – had made for "a bitter day, a day of mourning for democracy". But, speaking to fans waving the flags of his newly revived Forza Italia (FI) party, he said he would continue to "fight for our freedom" from the outside.

"We will stay on the field," he said, pointing to Beppe Grillo, figurehead of the M5S, and Matteo Renzi, the Florence mayor likely to become the next chief of the PD, as examples of leaders orchestrating their parties from outside the national parliament.

"My father has been stripped of his seat as senator, but it will certainly not be today's vote that will undermine his leadership and his commitment," said Marina Berlusconi, the media magnate's eldest daughter, who is regularly tipped by the Italian media as his most likely political heir – a prospect she rejects.

For the moment, Berlusconi will remain at the helm of the party named after a football chant, which he first launched for his entrance into politics in 1994. Replaced as the main centre-right party by the Freedom People (PdL) for several years until this summer, FI was reformed and, on Tuesday, moved into opposition by Berlusconi, who has seen his power base split by a breakaway faction led by an erstwhile loyalist, Angelino Alfano.

Alfano, the interior and deputy prime minister, has pledged his allegiance to Enrico Letta's government, which emerged stronger from a confidence vote on Tuesday.

Most analysts agree that, as old age and party splits combine with continuing legal woes, Berlusconi's farewell from politics is inevitable. Among other matters, he has been ordered to stand trial on charges of bribing a senator in an attempt to bring down Romano Prodi's government, and is appealing against a first-grade conviction handed down in June for having sex with an underage girl and abusing his office to cover it up. He denies the allegations in both cases.

But the question most observers ask is how long his goodbye will be - and nobody believes that the expulsion by itself will stop him. "It's certainly not the end for Berlusconi. He will join Beppe Grillo as a party leader outside of parliament and in 10 days time Matteo Renzi will be a party leader outside of parliament," said James Walston, of the American University of Rome. "Even when he's barred from taking part in politics, he'll take part in politics."